EP0015315A1 - Process for manufacture of silica by flame hydrolysis - Google Patents

Process for manufacture of silica by flame hydrolysis Download PDF

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Publication number
EP0015315A1
EP0015315A1 EP79104898A EP79104898A EP0015315A1 EP 0015315 A1 EP0015315 A1 EP 0015315A1 EP 79104898 A EP79104898 A EP 79104898A EP 79104898 A EP79104898 A EP 79104898A EP 0015315 A1 EP0015315 A1 EP 0015315A1
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Prior art keywords
water vapor
silica
thickening
silicas
flame
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German (de)
French (fr)
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EP0015315B1 (en
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Rudolf Dr. Schwarz
Peter Dr. Kleinschmit
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Evonik Operations GmbH
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Degussa GmbH
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/181—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process
    • C01B33/183—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process by oxidation or hydrolysis in the vapour phase of silicon compounds such as halides, trichlorosilane, monosilane
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/22—Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability

Definitions

  • silica in a pyrogenic way, for example by subjecting silicon tetrachloride to flame hydrolysis.
  • Silicic acids of this type are, for example, the different types of silicic acid available on the market under the name Aerosil R. They have different particle sizes in the range of 7 - 40 nm and can therefore be used for a wide variety of applications, such as thickening of liquid systems.
  • the typical parameter is usually not the particle size but the specific surface area in m 2 / g measured according to BET. If it is pore-free silicas, these two sizes correlate closely with each other.
  • This parameter depends on the BET surface area, so that with the known types of silica, which are produced by means of flame hydrolysis, a certain specific surface area can also be attributed to a certain thickening effect.
  • Vaporizable inorganic halogen compounds and / or organic halogen compounds of silicon can be used for this.
  • inorganic halogen compounds are SiH C 13 , siCl 2 H 2 , SiCl 4 and organic halogen compounds are CH 3 SiCl 3 , (CH 3 ) 2 SiCl 2 , ( CH 3 ) 3 SiCl, CH 3 -CH 2 -SiCl 3 or (CH 3 -CH 2 ) 2 SiCl 2 can be used.
  • the components hydrogen, oxygen or air and silicon tetrachloride are fed separately or premixed to a burner of the type shown schematically in US Pat. No. 2,990,249 and burned off at the burner outlet opening.
  • the amount of hydrogen is calculated in such a way that it is sufficient for a quantitative reaction of the chlorine atoms on the silicon atom with formation of hydrogen chloride when water vapor is formed. A small excess ensures that the reaction proceeds not only quantitatively, but also sufficiently quickly. It is not possible to set the excess of hydrogen as high as required, based on the amount of silicon tetrachloride.
  • the amount of excess hydrogen is limited by the fact that this reaction component is not only the component required for the hydrolysis of the chloride, but also the energy supplier. An excessively large increase in the excess of hydrogen would cause the temperature of the flame to rise, with disadvantageous consequences for the quality of the Si0 2 reaction products. It is possible to lower the reaction temperature by adding over-stoichiometric amounts of air or oxygen to the reaction mixture, with this measure is usually influenced the reaction temperature and thus the fine particle size or the specific surface of the reaction products is determined. There are limits to this possibility, however, because the outflow speed from the burner outlet opening has to be within relatively narrow limits and the increase in the amount of inert gas is thus at the expense of the system output.
  • the invention relates to a process for the controlled production of silica by means of flame hydrolysis, which is characterized in that additional amounts of water vapor, which do not result from the combustion of hydrogen or hydrogen-containing gases necessary for flame hydrolysis, are introduced into the reaction mixture.
  • the additional steam can be introduced in various ways.
  • the additional water vapor can be fed into the burner's mixing chamber via a separate line.
  • the additional water vapor can be introduced into the hydrogen or air supply to the burner and thus a hydrogen / water vapor mixture or an air / water vapor mixture Feed the burner.
  • the hydrogen or the oxygen-containing gas can be passed through a water evaporator at a temperature of from 20 ° C. to the boiling point of the water.
  • the additional water vapor of the gaseous silicon halide compound can be mixed in before it enters the burner, the temperature of the halosilane mixture having to be kept above the dew point in order to avoid silica deposits.
  • the additional water vapor can also be introduced into the flame, the location of the actual silica formation. This can be done by means of a probe which is passed axially through the burner and protrudes from the burner outlet opening, or via an annular nozzle with which the flame is surrounded. It is only essential that the mixing takes place as quickly and homogeneously as possible so that the influence of the additional water vapor on the reaction process and the formation of the silica can have a full effect, because the influence of the water vapor partial pressure decreases with the distance from the burner outlet opening.
  • a heat exchanger zone into which the flame gases are usually introduced there is no longer any influence on the formation of properties of the silica when additional amounts of water vapor are mixed in.
  • the admixed amount of water vapor can be varied within wide limits.
  • the water vapor is preferably introduced at a temperature of 150 to 250 ° C. and a pressure of 10 to 20 atm, in particular at a temperature of 185 to 210 ° C. and a pressure of 12 to 18 atm.
  • the ratio of water vapor to starting substance can be from 0.1 kg to 1 kg water vapor per kg starting substance.
  • hydrocarbon as fuel gas.
  • hydrocarbons can e.g. Be propane and / or butane.
  • a device can be used as the burner, as is shown in US Pat. No. 2,990,249. However, it is also possible to use a closed burner system in which no secondary air can penetrate the flame.
  • the specified thickening values were determined from a polyester reference system.
  • This polyester reference system is produced by mixing 80 parts by weight of Ludopal P 6 with 11.4 parts by weight of monostyrene and 7 parts by weight of styrene, which contains 1% paraffin. This system is also used for all other thickening determinations.
  • the overall property profile in particular the specific surface and the thickening behavior of the silicas obtained, shifts as the amount of water vapor supplied increases.
  • Curve a shows the correlation of the specific BET surface area with the thickening behavior of silicas, as is obtained in known processes by varying the excess air. This measure therefore only makes it possible to achieve a combination of properties of the silicas as already shown in FIG. 1.
  • the overall property profile, in particular the specific BET surface area and the thickening behavior, of the silicas obtained shifts as the amount of water vapor supplied increases.
  • Curve a shows the correlation of the specific BET surface area with the thickening behavior of silicas, as is obtained in known processes by varying the excess air.
  • the procedure is the same as that described in Example 1, but in addition to the substances specified there, 0.5 kg of steam per hour is used, which is introduced into the mixing chamber of the burner.
  • the silica that is obtained has a specific surface area of 466 m 2 and a thickening value of 3,910 mpascal.
  • Example 2 The procedure is as in Example 1, but an additional 1.8 kg of steam per hour, as described in Example 2, are added.
  • the silica has a surface area of 277 m 2 / g and a thickening value of 1,040 mpascal.
  • the procedure is as described in Example 1, but 0.5 kg of water vapor per hour is introduced into the flame axis at a distance of 1 cm from the burner outlet opening.
  • the silica has a specific surface area of 309 m 2 / g and a thickening value of 4,040 mpascal.
  • the procedure is as described in Examples 1 and 4, with the difference that 3 kg of water vapor are blown into the flame axis at a distance of 10 cm from the burner outlet opening.
  • the BET achieved for the silica is 212 m 2 / g and the thickening value is 1,105 mpascal.
  • Table I summarizes the determined values of the examples mentioned of the method according to the invention.

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  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Silicon Compounds (AREA)

Abstract

The controlled production of silicas by flame hydrolysis in which the thickening effect may be adjusted independently of the specific BET- surface of the silica obtained is achieved by introducing additional steam either into the reaction mixture or into the reaction flame.

Description

Es ist bekannt, Kieselsäure auf pyrogenem Wege herzustellen indem man z.B. Siliciumtetrachlorid einer Flammenhydrolyse unterwirft. Kieselsäuren dieser Art sind z.B. die unter der Bezeichnung AerosilR auf dem Markt befindlichen unterschiedlichen Kieselsäuretypen. Sie weisen unterschiedliche Teilchengrössen im Bereich von 7 - 40 nm auf und können infolgedessen für die unterschiedlichsten Anwendungszwecke, wie z.B. Verdickung von flüssigen Systemen, eingesetzt werden.It is known to produce silica in a pyrogenic way, for example by subjecting silicon tetrachloride to flame hydrolysis. Silicic acids of this type are, for example, the different types of silicic acid available on the market under the name Aerosil R. They have different particle sizes in the range of 7 - 40 nm and can therefore be used for a wide variety of applications, such as thickening of liquid systems.

Als typische Kenngrösse wird in der Regel nicht die Teilchengrösse sondern die spezifische Oberfläche in m2/g gemessen nach BET angegeben. Sofern es sich um porenfreie Kieselsäuren handelt, korrelieren diese beiden Grössen eng miteinander.The typical parameter is usually not the particle size but the specific surface area in m 2 / g measured according to BET. If it is pore-free silicas, these two sizes correlate closely with each other.

Eine ebenso wichtige Kenngrösse ist die Verdickungswirkung der verschiedenen Kieselsäuretypen in flüssigem System, weil der überwiegende Teil dieser Kieselsäuretypen als Verdickungs- und Thixotropierungsmittel eingesetzt werden.An equally important parameter is the thickening effect of the different types of silica in liquid System because the majority of these types of silica are used as thickeners and thixotropic agents.

Diese Kenngrösse steht in Abhängigkeit von der BET-Oberfläche, sodass bei den bekannten Kieselsäuretypen, welche mittels einer Flammenhydrolyse hergestellt werden, einer bestimmten spezifischen Oberfläche auch eine bestimmte Verdickungswirkung zugeschrieben werden kann.This parameter depends on the BET surface area, so that with the known types of silica, which are produced by means of flame hydrolysis, a certain specific surface area can also be attributed to a certain thickening effect.

Eine derartige Korrelation wird in der Graphik gemäss Fig. 1 dargestellt.Such a correlation is shown in the graph according to FIG. 1.

Bei den bekannten Verfahren der Flammenhydrolyse von Siliziumhalogenverbindungen in einer Wasserstoffflamme werden-gezeigt am Beispiel der Hydrolyse von Siliziumtetrachlorid- Luftbzw. Sauerstoff, Wasserstoff und Siliziumtetrachlorid-in einem solchen Verhältnis zueinander gemispht und abgebrannt, dass einerseits der Wasserstoff vollständig unter Bildung von Wasserdampf verbrennen und das Siliziumtetrachlorid andererseits quantitativ unter Bildung von SiO2 mit dem gebildeten Wasserdampf reagieren kann. Die nacheinander bzw. nebeneinander ablaufenden Reaktionen können durch die Gleichung . 1, 2 und 3 wiedergegeben werden:

Figure imgb0001
Figure imgb0002
Figure imgb0003
 In the known methods of flame hydrolysis of silicon halogen compounds in a hydrogen flame are shown using the example of the hydrolysis of silicon tetrachloride air or. Oxygen, hydrogen and silicon tetrachloride - misted and burned to one another in such a ratio that on the one hand the hydrogen burns completely with the formation of water vapor and on the other hand the silicon tetrachloride can react quantitatively with the water vapor formed to form SiO 2 . The successive or side-by-side reactions can be done by the equation. 1, 2 and 3 are reproduced:
Figure imgb0001
Figure imgb0002
Figure imgb0003

Diese Gleichungen gelten auch bei der Verwendung anderer Siliziumhalogenverbindungen als Ausgangsstoff.These equations also apply when other silicon halogen compounds are used as the starting material.

Dazu kann man verdampfbare anorganische Halogenverbindungen und/oder organische Halogenverbindungen des Siliciums verwenden.Vaporizable inorganic halogen compounds and / or organic halogen compounds of silicon can be used for this.

Als anorganische Halogenverbindungen sind beispielswei- se SiHCl3, siCl2H2, SiCl4 und als organische Halogenverbindungen CH3SiCl3, (CH3)2 SiCl2, (CH 3)3 SiCl, CH3-CH2-SiCl3 oder (CH3-CH2)2 SiCl2 einsetzbar. Examples of inorganic halogen compounds are SiH C 13 , siCl 2 H 2 , SiCl 4 and organic halogen compounds are CH 3 SiCl 3 , (CH 3 ) 2 SiCl 2 , ( CH 3 ) 3 SiCl, CH 3 -CH 2 -SiCl 3 or (CH 3 -CH 2 ) 2 SiCl 2 can be used.

Die Komponenten Wasserstoff, Sauerstoff bzw. Luft und Siliziumtetrachlorid werden zur Durchführung der Verbrennungshydrolyse einem Brenner des Typs, wie er in der US-PS 2 990 249 schematisch gezeichnet ist, getrennt oder vorgemischt zugeführt und an der Brenneraustrittsöffnung abgebrannt. Die Menge Wasserstoff ist so berechnet, dass sie unter Wasserdampfbildung für eine quantitative Reaktion der Chloratome am Siliziumatom unter Bildungen von Chlorwasserstoff ausreicht. Ein geringer Überschuss gewährleistet, dass der Reaktionsablauf nicht nur quantitativ, sondern auch ausreichend rasch erfolgt. Es ist nicht möglich, den Wasserstoffüberschuss, bezogen auf die Siliziumtetrachlorid-Menge beliebig hoch anzusetzen. Unabhängig davon, dass diese Massnahme die Verfahrenskosten unnötig verteuern würde, sind der Höhe des Wasserstoffüberschusses dadurch Grenzen gesetzt, dass diese Reaktionskomponente nicht nur die für die Hydrolyse des Chlorids erforderliche Komponente, sondern auch den Energielieferant darstellt. Eine zu grosse Erhöhung des Wasserstoffüberschusses würde bewirken, dass die Temperatur der Flamme mit nachteiligen Folgen für die Qualität der Si02-Reaktionsprodukte ansteigt. Es ist möglich, die Reaktionstemperatur durch Zugabe von überstöchiometrischen Mengen Luft bzw. Sauerstoff zu dem Reaktionsgemisch abzusenken, Mit dieser Massnahme wird üblicherweise die Reaktionstemperatur beeinflusst und damit die Feinteiligkeit bzw. die spezifische Oberfläche der Reaktionsprodukte festgelegt. Dieser Möglichkeit sind aber Grenzen gesetzt, weil die Ausströmgeschwindigkeit aus der Brenneraustrittsöffnung sich in relativ engen Grenzen bewegen muss und somit die Erhöhung der Inertgasmenge zu Lasten der Anlagenleistung geht.To carry out the combustion hydrolysis, the components hydrogen, oxygen or air and silicon tetrachloride are fed separately or premixed to a burner of the type shown schematically in US Pat. No. 2,990,249 and burned off at the burner outlet opening. The amount of hydrogen is calculated in such a way that it is sufficient for a quantitative reaction of the chlorine atoms on the silicon atom with formation of hydrogen chloride when water vapor is formed. A small excess ensures that the reaction proceeds not only quantitatively, but also sufficiently quickly. It is not possible to set the excess of hydrogen as high as required, based on the amount of silicon tetrachloride. Irrespective of the fact that this measure would make the process costs unnecessarily expensive, the amount of excess hydrogen is limited by the fact that this reaction component is not only the component required for the hydrolysis of the chloride, but also the energy supplier. An excessively large increase in the excess of hydrogen would cause the temperature of the flame to rise, with disadvantageous consequences for the quality of the Si0 2 reaction products. It is possible to lower the reaction temperature by adding over-stoichiometric amounts of air or oxygen to the reaction mixture, with this measure is usually influenced the reaction temperature and thus the fine particle size or the specific surface of the reaction products is determined. There are limits to this possibility, however, because the outflow speed from the burner outlet opening has to be within relatively narrow limits and the increase in the amount of inert gas is thus at the expense of the system output.

Das bekannte Verfahren zur Herstellung von Kieselsäuren mittel Flammenhydrolyse gemäss US-PS 2 990 249 weist nun den Nachteil auf, dass es mit ihm nicht gelingt, die Korrelation zwischen spezifischer Oberfläche und Verdickungsverhalten zu verändern und die Verdickungswirkung der Kieselsäure unabhängig von dem Wert der spezifischen Oberfläche einzustellen.The known method for the production of silicas by flame hydrolysis according to US Pat. No. 2,990,249 now has the disadvantage that it does not succeed in changing the correlation between the specific surface and the thickening behavior and the thickening effect of the silica regardless of the value of the specific surface adjust.

Gegenstand der Erfindung ist ein Verfahren zur gelenkten Herstellung von Kieselsäure mittels Flammenhydrolyse, welches dadurch gekennzeichnet ist, dass man in das Reaktionsgemisch zusätzliche Mengen an Wasserdampf, welche nicht aus der Verbrennung von für die Flammenhydrolyse notwendigen Wasserstoff oder Wasserstoff enthaltenden Gasen resultieren, einführt.The invention relates to a process for the controlled production of silica by means of flame hydrolysis, which is characterized in that additional amounts of water vapor, which do not result from the combustion of hydrogen or hydrogen-containing gases necessary for flame hydrolysis, are introduced into the reaction mixture.

Die Einführung des zusätzlichen Wasserdampfes kann auf verschiedene Art und Weise vorgenommen werden. So kann man den zusätzlichen Wasserdampf über eine separate Leitung in die Mischkammer des Brenners leiten. In einer anderen bevorzugten Variante des erfindungsgemässen Verfahrens kann man den zusätzlichen Wasserdampf in die Wasserstoff- bzw. die Luftzuführung zu dem Brenner einführen und somit ein Wasserstoff/Wasserdampf-Gemisch bzw. ein Luft/ Wasserdampf-Gemisch dem Brenner zuführen. Zur Vermischung mit Wasserdampf kann man den Wasserstoff bzw. das sauerstoffhaltige Gas bei einer Temperatur von 200C bis zur Siedetemperatur des Wassers durch einen Wasserverdampfer leiten.The additional steam can be introduced in various ways. In this way, the additional water vapor can be fed into the burner's mixing chamber via a separate line. In another preferred variant of the method according to the invention, the additional water vapor can be introduced into the hydrogen or air supply to the burner and thus a hydrogen / water vapor mixture or an air / water vapor mixture Feed the burner. To mix with water vapor, the hydrogen or the oxygen-containing gas can be passed through a water evaporator at a temperature of from 20 ° C. to the boiling point of the water.

In einer weiteren bevorzugten Variante kann man den zusätzlichen Wasserdampf der gasförmigen Siliciumhalogenverbindung vor deren Eintritt in den Brenner zumischen, wobei die Temperatur des Gemisches aus Halogensilan oberhalb des Taupunktes gehalten werden muss, um Kieselsäureabscheidungen zu vermeiden.In a further preferred variant, the additional water vapor of the gaseous silicon halide compound can be mixed in before it enters the burner, the temperature of the halosilane mixture having to be kept above the dew point in order to avoid silica deposits.

In einer weiteren bevorzugten Variante des erfindungsgemässen Verfahrens kann man den zusätzlichen Wasserdampf auch in die Flamme, den Ort der eigentlichen Kieselsäurebildung einleiten. Dies kann mittels einer Sonde geschehen, die man axial durch den Brenner hindurchführt und aus der Brenneraustrittsöffnung herausragen lässt, oder über eine Ringdüse, mit der man die Flamme umgibt. Wesentlich ist nur, dass die Einmischung möglichst rasch und homogen erfolgt, damit sich der Einfluss des zusätzlichen Wasserdampfes auf das Reaktionsgeschehen und die Bildung der Kieselsäure voll auswirken kann, denn der Einfluss des Wasserdampfpartialdruckes nimmt mit dem Abstand von der Brenneraustrittsöffnung ab. Am Ausgang des sogenannten Flammrohres, einer Wärmetauscherzone, in welche die Flammengase für gewöhnlich eingeleitet werden, ist kein Einfluss mehr auf das Eigenschaftsbildung der Kieselsäure bei Einmischung von zusätzlichen Wasserdampfmengen feststellbar.In a further preferred variant of the method according to the invention, the additional water vapor can also be introduced into the flame, the location of the actual silica formation. This can be done by means of a probe which is passed axially through the burner and protrudes from the burner outlet opening, or via an annular nozzle with which the flame is surrounded. It is only essential that the mixing takes place as quickly and homogeneously as possible so that the influence of the additional water vapor on the reaction process and the formation of the silica can have a full effect, because the influence of the water vapor partial pressure decreases with the distance from the burner outlet opening. At the exit of the so-called flame tube, a heat exchanger zone into which the flame gases are usually introduced, there is no longer any influence on the formation of properties of the silica when additional amounts of water vapor are mixed in.

Die zugemischte Wasserdampfmenge kann man in weiten Grenzen variieren.The admixed amount of water vapor can be varied within wide limits.

Vorzugsweise wird der Wasserdampf mit einer Temperatur von 150 bis 250°C und einem Druck von 10 bis 20 atü insbesondere mit einer Temperatur von 185 bis 210°C und einem Druck von 12 bis 18 atü eingeführt.The water vapor is preferably introduced at a temperature of 150 to 250 ° C. and a pressure of 10 to 20 atm, in particular at a temperature of 185 to 210 ° C. and a pressure of 12 to 18 atm.

Als Ausgangssubstanzen können alle bekannten anorganischen oder/und organischen Siliciumhalogenverbindungen eingesetzt werden.All known inorganic and / or organic silicon halogen compounds can be used as starting substances.

Das Verhältnis von Wasserdampf zu Ausgangssubstanz kann von 0,1 kg bis 1 kg Wasserdampf pro kg Ausgangssubstanz betragen.The ratio of water vapor to starting substance can be from 0.1 kg to 1 kg water vapor per kg starting substance.

In einer weiteren Ausführungsform der Erfindung kann man statt reinem Wasserstoff z.B. Kohlenwasserstoff als Brenngas einsetzen. Derartige Kohlenwasserstoffe können z.B. Propan und/oder Butan sein.In a further embodiment of the invention, instead of pure hydrogen, e.g. Use hydrocarbon as fuel gas. Such hydrocarbons can e.g. Be propane and / or butane.

Als Brenner kann man eine Vorrichtung verwenden, wie sie in der US-PS 2.990.249 dargestellt wird. Es ist aber auch die Verwendung eines geschlossenen Brennersystems, bei welchem keine Sekundärluft in die Flamme eindringen kann, möglich.A device can be used as the burner, as is shown in US Pat. No. 2,990,249. However, it is also possible to use a closed burner system in which no secondary air can penetrate the flame.

Die Steuerbarkeit der Verdickungswirkung ergibt sich aus den beigefügten Zeichnungen. Es zeigen

  • Fig. 1 die Abhängigkeit der Verdickungswirkung von der BET-Oberfläche bei bekannten Kieselsäuren
  • Fig. 2 die Abhängigkeit der Verdickungswirkung von der eingegebenen Wasserdampfmenge in Korrelation zu der BET-Oberfläche bei Kieselsäuren, die gemäss dem erfindungsgemässen Verfahren hergestellt werden, wobei der zusätzliche Wasserdampf in die Reaktionsmischung vor der Brennkammer zugegeben wird.
  • Fig. 3 die Abhängigkeit der Verdickungswirkung von der eingegebenen Wasserdampfmenge in Korrelation zu der BET-Oberfläche bei Kieselsäuren, die gemäss dem erfindungsgemässen Verfahren hergestellt werden, wobei der zusätzliche Wasserdampf in die Brennerflamme zugegeben wird.
The controllability of the thickening effect is evident from the accompanying drawings. Show it
  • Fig. 1 shows the dependence of the thickening effect on the BET surface in known silicas
  • Fig. 2 shows the dependence of the thickening effect on the amount of water vapor entered in correlation to the BET surface area for silicas, according to the inventive method are produced, the additional water vapor being added to the reaction mixture upstream of the combustion chamber.
  • 3 shows the dependence of the thickening effect on the amount of water vapor entered in correlation to the BET surface area in the case of silicas which are produced in accordance with the method according to the invention, the additional water vapor being added to the burner flame.

Gemäss der Fig. 1 wird die Abhängigkeit der Verdickungswirkung von der BET-Oberfläche bei Kieselsäuren graphisch dargestellt, welche nach bekannten Verfahren hergestellt wurden. Für die einzelnen Kieselsäuren ergeben sich die folgenden Werte:

Figure imgb0004
1, the dependence of the thickening effect on the BET surface area for silicas which have been produced by known processes is shown graphically. The following values result for the individual silicas:
Figure imgb0004

Die genannten Verdickungswerte wurden aus einem Polyester-Bezugssystem ermittelt.The specified thickening values were determined from a polyester reference system.

Dieses Polyester-Bezugssystem wird hergestellt, indem man 80 Gew.-Teile Ludopal P 6 mit 11,4 Gew.-Teilen Monostyrol und 7 Gew.-Teilen Styrol, welches 1 % Paraffin enthält, vermischt. Dieses System wird bei allen weiteren Verdickungsbestimmungen ebenfalls verwendet.This polyester reference system is produced by mixing 80 parts by weight of Ludopal P 6 with 11.4 parts by weight of monostyrene and 7 parts by weight of styrene, which contains 1% paraffin. This system is also used for all other thickening determinations.

Gemäss der Fig. 2 verschiebt sich mit steigender zugeführter Wasserdampfmenge das gesamte Eigenschaftsbild insbesondere die spezifische Oberfläche und das Verdickungsverhalten der erhaltenen Kieselsäuren.According to FIG. 2, the overall property profile, in particular the specific surface and the thickening behavior of the silicas obtained, shifts as the amount of water vapor supplied increases.

So zeigt die Kurve a) die Korrelation von spezifischer BET-Oberfläche mit dem Verdickungsverhalten von Kieselsäuren, wie sie bei bekannten Verfahren durch Variation des Luftüberschusses erhalten wird. Durch diese Massnahme ist es also nur möglich, eine wie bereits in Fig. 1 dargestellte Eigenschaftskombination der Kieselsäuren zu erzielen.Curve a) shows the correlation of the specific BET surface area with the thickening behavior of silicas, as is obtained in known processes by varying the excess air. This measure therefore only makes it possible to achieve a combination of properties of the silicas as already shown in FIG. 1.

Aus der Kurve b) lässt sich dagegen erkennen, dass sowohl das Verdickungsverhalten als auch die spezifische BET-Oberfläche der mittels dem erfindungsgemässen Verfahren erhaltenene Kieselsäuren mit steigender Wasserdampfeinführung in die Reaktionsmischung vor der Verbrennung in Vergleich zu einer Grundeinstellung zunächst weit über die Werte, wie sie von den bekannten Kieselsäuren gemäss der Kurve a) bekannt sind, hinauslaufen, um dann mit grösseren Wasserdampfmengen stark abzusinken, wobei neue Eigenschaftskombinationen erreicht werden. So ist es z.B. möglich, Kieselsäuren mit gleicher BET-Oberfläche aber stark unterschiedlichem Verdickungsverhalten herzustellen.From curve b), on the other hand, it can be seen that both the thickening behavior and the specific BET surface area of the silicas obtained by means of the process according to the invention with increasing introduction of water vapor into the reaction mixture prior to combustion compared to a basic setting initially far above the values as they are known of the known silicas according to curve a), then run out with large amounts of water vapor to sink, new combinations of properties being achieved. For example, it is possible to produce silicas with the same BET surface area but very different thickening behavior.

Gemäss der Fig. 3 verschiebt sich mit steigender zugeführter Wasserdampfmenge das gesamte Eigenschaftsbild, insbesondere die spezifische BET-Oberfläche und das Verdickungsverhalten, der erhaltenen Kieselsäuren.According to FIG. 3, the overall property profile, in particular the specific BET surface area and the thickening behavior, of the silicas obtained shifts as the amount of water vapor supplied increases.

So zeigt die Kurve a) die Korrelation von spezifischer BET-Oberfläche mit dem Verdickungsverhalten von Kieselsäuren, wie sie bei bekannten Verfahren durch Variation des Luftüberschusses erhalten wird. Durch diese Massnahme ist es also nur möglich, wie bereits in den Figuren 1 und 2 ausgeführt, eine Eigenschafskombination zu erzielen, bei der die Verdickungswirkung von der spezifischen BET-Oberfläche abhängig ist.Curve a) shows the correlation of the specific BET surface area with the thickening behavior of silicas, as is obtained in known processes by varying the excess air. As a result of this measure, it is only possible, as already explained in FIGS. 1 and 2, to achieve a combination of properties in which the thickening effect depends on the specific BET surface area.

Aus der Kurve b) lässt sich dagegen erkennen, dass sowohl das Verdickungsverhalten als auch die spezifische BET-Oberfläche der mittels dem erfindungsgemässen Verfahren erhaltenen Kieselsäuren mit steigender Wasserdampfeinführung in die Flamme im Vergleich zu einer Grundeinstellung völlig verschieden zu der den bekannten Kieselsäuren entsprechenden Kurve a) verlaufen. Dabei können neue Eigenschaftskombinationen erreicht werden.On the other hand, it can be seen from curve b) that both the thickening behavior and the specific BET surface area of the silicas obtained by means of the process according to the invention with increasing introduction of water vapor into the flame compared to a basic setting completely different from the curve a) corresponding to the known silicas run. New combinations of properties can be achieved.

So ist es zoB. möglich, Kieselsäuren mit gleicher BET-Oberfläche aber stark unterschiedlichem Verdickungsverhalten herzustellen:

  • Das erfindungsgemässe Verfahren wird anhand der folgenden Beispiele näher erläutert und beschrieben:
So it is zoB. possible to produce silicas with the same BET surface area but very different thickening behavior:
  • The process according to the invention is explained and described in more detail using the following examples:

Beispiel 1example 1

6,2 kg Siliziumtetrachlorid werden verdampft und mit 2,2 m3 Wasserstoff und 5,8 m3 Luft in der Mischkammer eines Brenners vermischt. Das Gasgemisch brennt aus der Austrittsöffnung und Wird mittels Unterdruck in das Kühlsystem eingesaugt. Nach der Abtrennung von dem Chlorwasserstoff-haltigen Gasgemisch erhält man 2,2 kg einer hochdispersen Kieselsäure, die eine spezifische Oberfläche von 200 m2/g und eine Verdickung eines Polyesterbezugssystemes von 3.100 mpascal aufweist.6.2 kg of silicon tetrachloride are evaporated and mixed with 2.2 m 3 of hydrogen and 5.8 m 3 of air in the mixing chamber of a burner. The gas mixture burns from the outlet opening and is sucked into the cooling system by means of negative pressure. After separation from the hydrogen chloride-containing gas mixture, 2.2 kg of a highly disperse silica are obtained, which has a specific surface area of 200 m 2 / g and a thickening of a polyester reference system of 3,100 mpascal.

Beispiel 2Example 2

Man verfährt in gleicher Weise wie unter Beispiel 1 beschrieben, setzt aber zusätzlich zu den dort angegebenen Stoffen 0,5 kg Wasserdampf pro Stunde ein, die man in die Mischkammer des Brenners einleitet. Die Kieselsäure, die man erhält, weist eine spezifische Oberfläche von 466 m2 und einen Verdickungswert von 3.910 mpascal auf.The procedure is the same as that described in Example 1, but in addition to the substances specified there, 0.5 kg of steam per hour is used, which is introduced into the mixing chamber of the burner. The silica that is obtained has a specific surface area of 466 m 2 and a thickening value of 3,910 mpascal.

Beispiel 3Example 3

Man verfährt wie unter Beispiel 1, setzt aber zusätzlich 1,8 kg Wasserdampf pro Stunde, wie unter Beispiel 2 beschrieben,zu. Die Kieselsäure besitzt die Oberfläche von 277 m2/g und einen Verdickungswert von 1.040 mpascal.The procedure is as in Example 1, but an additional 1.8 kg of steam per hour, as described in Example 2, are added. The silica has a surface area of 277 m 2 / g and a thickening value of 1,040 mpascal.

Beispiel 4Example 4

Man verfährt wie unter Beispiel 1 beschrieben, führt aber mit einer Sonde 0,5 kg Wasserdampf pro Stunde in die Flammenachse ein, in einem Abstand von 1 cm von der Brenneraustrittsöffnung. Die Kieselsäure weist eine.spezifische Oberfläche von 309 m2/g und einen Verdickungswert von 4.040 mpascal auf.The procedure is as described in Example 1, but 0.5 kg of water vapor per hour is introduced into the flame axis at a distance of 1 cm from the burner outlet opening. The silica has a specific surface area of 309 m 2 / g and a thickening value of 4,040 mpascal.

Beispiel -5Example -5

Man verfährt wie in Beispiel 1 und 4 beschrieben mit dem Unterschied, dass 3 kg Wasserdampf in die Flammenachse im Abstand von 10 cm von der Brenneraustrittsöffnung eingeblasen werden. Die erzielte BET der Kieselsäure liegt bei 212 m2/g und der Verdickungswert bei 1.105 mpascal.The procedure is as described in Examples 1 and 4, with the difference that 3 kg of water vapor are blown into the flame axis at a distance of 10 cm from the burner outlet opening. The BET achieved for the silica is 212 m 2 / g and the thickening value is 1,105 mpascal.

Die Tabelle I fasst die ermittelten Werte der genannten Beispiele des erfindungsgemässen Verfahrens zusammen.Table I summarizes the determined values of the examples mentioned of the method according to the invention.

Die Werte für die spezifische Oberfläche und die Verdickung entsprechend den Kurven b) in den Figuren 2 und 3.

Figure imgb0005
Figure imgb0006
 The values for the specific surface area and the thickening in accordance with curves b) in FIGS. 2 and 3.
Figure imgb0005
Figure imgb0006

Claims (1)

Verfahren zur gelenkten Herstellung von Kieselsäure mittels Flammenhydrolyse, dadurch gekennzeichnet, dass man in das Reaktionsgemisch zusätzliche Mengen an Wasserdampf, welche nicht aus der Verbrennung von für die Flammenhydrolyse notwendigen Wasserstoff enthaltenden Gasen resultieren, einführt.Process for the controlled production of silica by means of flame hydrolysis, characterized in that additional amounts of water vapor which do not result from the combustion of gases containing hydrogen necessary for flame hydrolysis are introduced into the reaction mixture.
EP79104898A 1979-02-05 1979-12-04 Process for manufacture of silica by flame hydrolysis Expired EP0015315B1 (en)

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DE19792904199 DE2904199A1 (en) 1979-02-05 1979-02-05 METHOD FOR THE GUIDED PRODUCTION OF SILICON BY MEANS OF FLAME HYDROLYSIS

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EP0092024A1 (en) * 1980-04-25 1983-10-26 Degussa Aktiengesellschaft Silica prepared in the pyrogenic way, and process for its preparation
US10618833B2 (en) 2015-12-18 2020-04-14 Heraeus Quarzglas Gmbh & Co. Kg Preparation of a synthetic quartz glass grain
US10676388B2 (en) 2015-12-18 2020-06-09 Heraeus Quarzglas Gmbh & Co. Kg Glass fibers and pre-forms made of homogeneous quartz glass
US10730780B2 (en) 2015-12-18 2020-08-04 Heraeus Quarzglas Gmbh & Co. Kg Preparation of a quartz glass body in a multi-chamber oven
US11053152B2 (en) 2015-12-18 2021-07-06 Heraeus Quarzglas Gmbh & Co. Kg Spray granulation of silicon dioxide in the preparation of quartz glass
US11236002B2 (en) 2015-12-18 2022-02-01 Heraeus Quarzglas Gmbh & Co. Kg Preparation of an opaque quartz glass body
US11299417B2 (en) 2015-12-18 2022-04-12 Heraeus Quarzglas Gmbh & Co. Kg Preparation of a quartz glass body in a melting crucible of refractory metal
US11339076B2 (en) 2015-12-18 2022-05-24 Heraeus Quarzglas Gmbh & Co. Kg Preparation of carbon-doped silicon dioxide granulate as an intermediate in the preparation of quartz glass
US11492282B2 (en) 2015-12-18 2022-11-08 Heraeus Quarzglas Gmbh & Co. Kg Preparation of quartz glass bodies with dew point monitoring in the melting oven
US11492285B2 (en) 2015-12-18 2022-11-08 Heraeus Quarzglas Gmbh & Co. Kg Preparation of quartz glass bodies from silicon dioxide granulate
US11952303B2 (en) 2015-12-18 2024-04-09 Heraeus Quarzglas Gmbh & Co. Kg Increase in silicon content in the preparation of quartz glass

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DE3028364C2 (en) * 1980-07-26 1983-07-21 Degussa Ag, 6000 Frankfurt Process and apparatus for the pyrogenic production of silicon dioxide
JPS5788020A (en) * 1980-11-14 1982-06-01 Ube Ind Ltd Manufacture of very finely grained anhydrous silica
GB8905966D0 (en) * 1989-03-15 1989-04-26 Tsl Group Plc Improved vitreous silica products
DE10163939A1 (en) * 2001-12-22 2003-07-10 Degussa Layer obtained from an aqueous dispersion containing flame-hydrolytically produced silicon-titanium mixed oxide powder
DE10312970A1 (en) * 2003-03-24 2004-10-14 Degussa Ag Fumed silica powder and dispersion thereof
DE10326049A1 (en) * 2003-06-10 2004-12-30 Degussa Ag Flame hydrolytically produced silicon dioxide, process for its production and use
DE102005001408A1 (en) * 2005-01-12 2006-07-20 Degussa Ag Pyrogenic silica powder

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0092024A1 (en) * 1980-04-25 1983-10-26 Degussa Aktiengesellschaft Silica prepared in the pyrogenic way, and process for its preparation
US10618833B2 (en) 2015-12-18 2020-04-14 Heraeus Quarzglas Gmbh & Co. Kg Preparation of a synthetic quartz glass grain
US10676388B2 (en) 2015-12-18 2020-06-09 Heraeus Quarzglas Gmbh & Co. Kg Glass fibers and pre-forms made of homogeneous quartz glass
US10730780B2 (en) 2015-12-18 2020-08-04 Heraeus Quarzglas Gmbh & Co. Kg Preparation of a quartz glass body in a multi-chamber oven
US11053152B2 (en) 2015-12-18 2021-07-06 Heraeus Quarzglas Gmbh & Co. Kg Spray granulation of silicon dioxide in the preparation of quartz glass
US11236002B2 (en) 2015-12-18 2022-02-01 Heraeus Quarzglas Gmbh & Co. Kg Preparation of an opaque quartz glass body
US11299417B2 (en) 2015-12-18 2022-04-12 Heraeus Quarzglas Gmbh & Co. Kg Preparation of a quartz glass body in a melting crucible of refractory metal
US11339076B2 (en) 2015-12-18 2022-05-24 Heraeus Quarzglas Gmbh & Co. Kg Preparation of carbon-doped silicon dioxide granulate as an intermediate in the preparation of quartz glass
US11492282B2 (en) 2015-12-18 2022-11-08 Heraeus Quarzglas Gmbh & Co. Kg Preparation of quartz glass bodies with dew point monitoring in the melting oven
US11492285B2 (en) 2015-12-18 2022-11-08 Heraeus Quarzglas Gmbh & Co. Kg Preparation of quartz glass bodies from silicon dioxide granulate
US11708290B2 (en) 2015-12-18 2023-07-25 Heraeus Quarzglas Gmbh & Co. Kg Preparation of a quartz glass body in a multi-chamber oven
US11952303B2 (en) 2015-12-18 2024-04-09 Heraeus Quarzglas Gmbh & Co. Kg Increase in silicon content in the preparation of quartz glass

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IT7969244A0 (en) 1979-11-20
FR2447887A1 (en) 1980-08-29
ATE4303T1 (en) 1983-08-15
CA1179477A (en) 1984-12-18
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FR2447887B1 (en) 1984-09-07
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GB2044738B (en) 1983-05-11
CH642931A5 (en) 1984-05-15
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EP0015315B1 (en) 1983-07-27
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LU81909A1 (en) 1980-04-22

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